These small plants are of unusual appearance and do not resemble common ferns. Common names include water clover and four-leaf clover because of the long-stalked leaves have four clover-like lobes and are either present above water or submerged.

The sporocarps of some Australian species are very drought-resistant, surviving up to 100 years in dry conditions. On wetting, the gelatinous interior of the sporocarp swells, splitting it and releasing a worm-like mass that carries sori, eventually leading to germination of spores and fertilization.

Sporocarps of some Australian species such as Marsilea drummondii are edible and have been eaten by Aborigines and early white settlers, who knew it under the name ngardu or nardoo. Parts of Marsilea drummondii contain an enzyme which destroys thiamine (vitamin B1), leading to brain damage in sheep and horses. During floods in the Gwydir River basin 2,200 sheep died after eating nardoo. Three-quarters of the sheep that were affected did however respond to thiamine injections.[5]Thiamine deficiency from incorrectly prepared nardoo likely resulted in the starvation and death of Burke and Wills.[6][7]